Practice of Epidemiology Association Between Questionnaire- and Accelerometer-Assessed Physical Activity: The Role of Sociodemographic Factors

The correlation between objective and self-reported measures of physical activity varies between studies. We examined this association and whether it differed by demographic factors or socioeconomic status (SES). Data were from 3,975Whitehall II (United Kingdom, 2012–2013) participants aged 60–83 years, who completed a phys-ical activity questionnaire and wore an accelerometer on their wrist for 9 days. There was a moderate correlation between questionnaire- and accelerometer-assessed physical activity (Spearman’s r = 0.33, 95 % confidence inter-val: 0.30, 0.36). The correlations were higher in high-SES groups than in low-SES groups (P ’s = 0.02), as defined by education (r = 0.38 vs. r = 0.30) or occupational position (r = 0.37 vs. r = 0.29), but did not differ by age, sex, or mar-ital status. Of the self-reported physical activity, 68.3 % came frommild activities, 25 % frommoderate activities, and only 6.7 % from vigorous activities, but their correlations with accelerometer-assessed total physical activity were comparable (range of r ’s, 0.21–0.25). Self-reported physical activity from more energetic activities was more strongly associated with accelerometer data (for sports, r = 0.22; for gardening, r = 0.16; for housework, r = 0.09). High-SES persons reported more energetic activities, producing stronger accelerometer associations in these groups. Future studies should identify the aspects of physical activity that are most critical for health; this involves better understanding of the instruments being used. accelerometry; cohort studies; elderly; epidemiologic methods; physical activity; questionnaire